Origin of eclogite‐bearing, domed, layered metamorphic complexes (“core complexes”) in the D'entrecasteaux Islands, Papua New Guinea

Abstract

Compositionally layered metamorphic rocks of the D'Entrecasteaux Islands, Papua New Guinea, are folded into domes and antiforms bounded by faults parallel to metamorphic layering and foliation.The structures are broadly similar to the metamorphic "core complexes" of western North America.

Can microplate rotation drive subduction inversion

“…In other words, horizontal plate motion locally results in normal-sense reactivation of the subduction thrust and unbending of the lower plate as it is exhumed. This concept is supported by the megamullioned and domal morphology and apparent rolling-hinge style kinematics of shear zones on Normanby Island (Little et al, 2007) and the Dayman Dome (Davies and Warren, 1988). The term "subduction inversion" is used to denote the exhumation of the subduction complex due to the normal-sense reactivation of the subduction thrust.…”

“…Lineations in gneisses in the domes on Goodenough and western Fergusson Islands (Hill, 1994) are more variable and locally are oblique to the Pliocene plate motion vector. On the northern dip-slope of the Dayman Dome, an incipient metamorphic core complex (Davies and Warren, 1988), lineations trend approximately parallel to the presentday Woodlark-Australia plate motion vector. Available data indicate that structures associated with exhumation are still active (Abers, 2001).…”

“…The HP-UHP rocks are found in the lower plates of metamorphic core complexes distributed along the Australian-Woodlark plate boundary (Davies, 1980a,b;Davies and Warren, 1988;Worthing, 1988;Hill and Baldwin, 1993;Little et al, 2007;Appleby, 1996;Peters, 2007). Footwall blueschist, eclogite, migmatite, gneiss, and Pliocene granodiorite are juxtaposed against an upper plate consisting of the Papuan Ultramafi c Belt, unmetamorphosed sediments, and volcanic rocks (Davies and Warren , 1988;Hill et al, 1992;Hill, 1994, Little et al, 2007.…”

“…Footwall blueschist, eclogite, migmatite, gneiss, and Pliocene granodiorite are juxtaposed against an upper plate consisting of the Papuan Ultramafi c Belt, unmetamorphosed sediments, and volcanic rocks (Davies and Warren , 1988;Hill et al, 1992;Hill, 1994, Little et al, 2007. Exhumation of HP-UHP rocks was facilitated by top-to-the-N (or NE), kilometer-scale ductile shear zones and normal faults on the northern fl anks of the antiformal domes (Davies and Warren, 1988;Hill, 1994;Little et al, 2007). Stretching lineations in mylonites on Normanby Island and in gneisses on the eastern part of Fergusson Island trend N or NNE, roughly parallel to 3.6-0.5 Ma plate motion vectors (Fig.…”

Evidence for seismogenic normal faults at shallow dips in continental rifts

“…Mutter et al 1996;Taylor et al 1999). The continental section features development of several metamorphic core complexes along the rift (Davies & Warren 1988). Extension takes place about a pole somewhere west of 147°E, with rates in the continental section ranging from 10 to 40mm a -1 (Taylor et al 1999 (Davies & Warren 1988) and appears to be active (Ollier& Pain 1980).…”